Conventional rare earth magnets including fluoride compounds are described, for example, in JP-A-2003-282312. In the technology described in JP-A-2003-282312, the grain boundary phase has a granular fluoride compound, and the size of the grain of the grain boundary phase is several μm. In such a rare earth magnet, if the coercive force is enhanced, the energy product decreases significantly.
Patent literature 1: JP-A-2003-282312
In the patent literature 1, the magnetic properties of a sintered magnet produced by adding NdFeB powder for sintered magnet and DyF3 that is a fluoride compound is described in table 3. Value of a residual magnetic flux density (Br) is 11.9 kG when DyF3 is added by 5 wt %. The value is decreased by about 9.8% as compared to a value (13.2 kG) of the case of no addition thereof. The energy product ((BH)max) also decreases significantly due to the decrease of the residual magnetic flux density. Therefore, though the coercive force is increased, it is difficult to use the magnet for a magnetic circuit requiring high magnetic flux or a rotating machine requiring high torque due to the small energy product.
In the patent literature 1, as for NdF3, it is used by mixing NdF3 powder having a mean particle diameter of 0.2 μm and NdFeB alloy powder using an automatic mortar, but there is no description in relation to the shape of the fluoride, and after sintering it is aggregated.